1. Technical Field
The present disclosure relates to surgical sutures and more particularly to coatings for sutures and fluids in which sutures are stored and/or packaged.
2. Background of Related Art
Absorbable sutures are manufactured from natural or synthetic materials. Some of the earliest absorbable sutures were made of collagenous material taken from sheep intestines. Such sutures are still in use today and are commonly referred to as catgut or gut sutures or ligatures. In the present specification, gut suture refers to a collagen based suture or ligature of any type or origin. Gut sutures may be prepared in the form of threads or strands that are undesirably stiff before subsequent treatment which renders them flexible or pliable. Flexibility and pliability are important to allow efficient manipulation of the suture by the surgeon during an operation.
A suture having a good degree of flexibility and pliability can conform closely to body tissue without undue pressure. Good flexibility and pliability enhance the degree to which a suture can be tied down, knotted and securely placed in a desired position. Various attempts have been made to modify and optimize the physical characteristics of gut sutures. For example, tubing fluids are liquids which are used to condition gut sutures to achieve or enhance flexibility and pliability. Tubing fluids are also used to preserve gut sutures. Tubing fluids typically contain an alcohol such as isopropyl alcohol and a relatively small percentage of water. Examples of tubing fluids are found in U.S. Pat. Nos. 1,239,690, 2,394,054, 2,519,404, 2,524,772, and 2,694,487. Ideally, the tubing fluid aids the gut suture to retain its flexibility and pliability without adversely affecting the strength and overall integrity of the suture.
Commercially available gut sutures are immersed in tubing fluid, sterilized and supplied to surgeons in packages or tubes which contain tubing fluid (hence the name tubing fluids). The alcohol and water keep the suture flexible and pliable as long as they remain in contact with the suture. As the tubing fluid evaporates, the suture loses its flexibility and pliability which may affect handling characteristics.
In addition to tubing fluids, various suture coatings which adhere to the surface of the suture have been developed in an attempt to maintain flexibility and control swelling and fraying. Such coatings are also intended to improve the handling characteristics of sutures and maximize run-down performance. For example, lubricants which are employed to permit slippage between collagen filaments of a multifilament thread or strand are described in U.S. Pat. No. 2,576,576. Such lubricants include fatty oils such as polyhydric alcoholesters of such fatty acids as stearic acid, oleic acid, linoleic acid, and myristic acid. U.S. Pat. No. 3,478,140 is directed to applying a solution of dehydrated castor oil in hexane or an emulsion of dehydrated castor oil to reconstituted collagen strands and then drying the strands under heat and tension for surface coating. Another castor oil containing emulsion which is dried onto collagen sutures is described in U.S. Pat. No. 3,413,079. Yet another coating composition containing castor oil is described in U.S. Pat. No. 4,027,676. In U.S. Pat. No. 4,185,637, a composition containing a gel of a fatty acid salt such as calcium stearate is described as being deposited on the surface of a suture by solvent evaporation to form a coating. Sutures which have been treated with a coating lubricant containing stearic acid or calcium stearate are compared in U.S. Pat. No. 4,201,216. The stearic acid lubricant has a much lower tie-down rating than calcium stearate lubricant.